package lan.reflect;

import java.lang.reflect.*;
import java.util.Set;

/** Provides reflective access to the constant pools of classes.
 Currently this is needed to provide reflective access to annotations
 but may be used by other internal subsystems in the future. */

public class ConstantPool {
    // Number of entries in this constant pool (= maximum valid constant pool index)
    public int      getSize()                      { return getSize0            (constantPoolOop);        }
    public Class<?> getClassAt         (int index) { return getClassAt0         (constantPoolOop, index); }
    public Class<?> getClassAtIfLoaded (int index) { return getClassAtIfLoaded0 (constantPoolOop, index); }
    // Returns a class reference index for a method or a field.
    public int getClassRefIndexAt(int index) {
        return getClassRefIndexAt0(constantPoolOop, index);
    }
    // Returns either a Method or Constructor.
    // Static initializers are returned as Method objects.
    public Member   getMethodAt        (int index) { return getMethodAt0        (constantPoolOop, index); }
    public Member   getMethodAtIfLoaded(int index) { return getMethodAtIfLoaded0(constantPoolOop, index); }
    public Field    getFieldAt         (int index) { return getFieldAt0         (constantPoolOop, index); }
    public Field    getFieldAtIfLoaded (int index) { return getFieldAtIfLoaded0 (constantPoolOop, index); }
    // Fetches the class name, member (field, method or interface
    // method) name, and type descriptor as an array of three Strings
    public String[] getMemberRefInfoAt (int index) { return getMemberRefInfoAt0 (constantPoolOop, index); }
    // Returns a name and type reference index for a method, a field or an invokedynamic.
    public int getNameAndTypeRefIndexAt(int index) {
        return getNameAndTypeRefIndexAt0(constantPoolOop, index);
    }
    // Fetches the name and type from name_and_type index as an array of two Strings
    public String[] getNameAndTypeRefInfoAt(int index) {
        return getNameAndTypeRefInfoAt0(constantPoolOop, index);
    }
    public int      getIntAt           (int index) { return getIntAt0           (constantPoolOop, index); }
    public long     getLongAt          (int index) { return getLongAt0          (constantPoolOop, index); }
    public float    getFloatAt         (int index) { return getFloatAt0         (constantPoolOop, index); }
    public double   getDoubleAt        (int index) { return getDoubleAt0        (constantPoolOop, index); }
    public String   getStringAt        (int index) { return getStringAt0        (constantPoolOop, index); }
    public String   getUTF8At          (int index) { return getUTF8At0          (constantPoolOop, index); }
    public Tag getTagAt(int index) {
        return Tag.valueOf(getTagAt0(constantPoolOop, index));
    }

    public static enum Tag {
        UTF8(1),
        INTEGER(3),
        FLOAT(4),
        LONG(5),
        DOUBLE(6),
        CLASS(7),
        STRING(8),
        FIELDREF(9),
        METHODREF(10),
        INTERFACEMETHODREF(11),
        NAMEANDTYPE(12),
        METHODHANDLE(15),
        METHODTYPE(16),
        INVOKEDYNAMIC(18),
        INVALID(0);

        private final int tagCode;

        private Tag(int tagCode) {
            this.tagCode = tagCode;
        }

        private static Tag valueOf(byte v) {
            for (Tag tag : Tag.values()) {
                if (tag.tagCode == v) {
                    return tag;
                }
            }
            throw new IllegalArgumentException("Unknown constant pool tag code " + v);
        }
    }
    //---------------------------------------------------------------------------
    // Internals only below this point
    //

    static {
        Reflection.registerFieldsToFilter(ConstantPool.class, Set.of("constantPoolOop"));
    }

    // HotSpot-internal constant pool object (set by the VM, name known to the VM)
    private Object constantPoolOop;

    private native int      getSize0            (Object constantPoolOop);
    private native Class<?> getClassAt0         (Object constantPoolOop, int index);
    private native Class<?> getClassAtIfLoaded0 (Object constantPoolOop, int index);
    private native int      getClassRefIndexAt0 (Object constantPoolOop, int index);
    private native Member   getMethodAt0        (Object constantPoolOop, int index);
    private native Member   getMethodAtIfLoaded0(Object constantPoolOop, int index);
    private native Field    getFieldAt0         (Object constantPoolOop, int index);
    private native Field    getFieldAtIfLoaded0 (Object constantPoolOop, int index);
    private native String[] getMemberRefInfoAt0 (Object constantPoolOop, int index);
    private native int      getNameAndTypeRefIndexAt0(Object constantPoolOop, int index);
    private native String[] getNameAndTypeRefInfoAt0(Object constantPoolOop, int index);
    private native int      getIntAt0           (Object constantPoolOop, int index);
    private native long     getLongAt0          (Object constantPoolOop, int index);
    private native float    getFloatAt0         (Object constantPoolOop, int index);
    private native double   getDoubleAt0        (Object constantPoolOop, int index);
    private native String   getStringAt0        (Object constantPoolOop, int index);
    private native String   getUTF8At0          (Object constantPoolOop, int index);
    private native byte     getTagAt0           (Object constantPoolOop, int index);
}
